API C90 Casing vs API L80 Casing
These two grades are listed as equivalents of each other: their chemistry windows overlap and they serve the same applications. They are not always identical — check the differences below before substituting, especially in certified designs.
API C90 Casing
Pipe & Tube Steel
C90 is a controlled-hardness API 5CT grade for sour (H₂S) wells: quenched-and-tempered to a 90 ksi yield window while the hardness is capped at 25.4 HRC so sulfide stress cracking cannot start. It is specified where N80-type material would be an SSC risk.
Standards: AISI API 5CT C90 · GB C90 (GB/T 19830)
API L80 Casing
Pipe & Tube Steel
L80 is the sour-service-capable API 5CT grade: same 80 ksi class as N80 but with a controlled yield window and a 23 HRC hardness cap that resists sulfide stress cracking. Type 1 is the standard Cr-free version; 9Cr and 13Cr types cover corrosive CO2 service.
Standards: AISI API 5CT L80 (Type 1) · GB L80 (GB/T 19830)
Chemical composition compared (%)
| Element | API C90 Casing | API L80 Casing |
|---|---|---|
| P | ≤0.030 | ≤0.030 |
| S | ≤0.030 | ≤0.030 |
| Note | API 5CT controls C90 by strength, hardness and SSC testing — no C/Mn composition limits | Hardness capped at 23 HRC for sour-service suitability |
| C | — | ≤0.43 (Type 1) |
| Mn | — | ≤1.90 (Type 1) |
Properties compared
| Property | API C90 Casing | API L80 Casing |
|---|---|---|
| Yield strength | 621–758 MPa (90–105 ksi) | 552–655 MPa (80–95 ksi, controlled band) |
| Tensile strength | ≥689 MPa (100 ksi) | ≥655 MPa (95 ksi) |
| Hardness | ≤25.4 HRC (sour-service cap) | ≤23 HRC |
| Density | 7.85 g/cm³ | 7.85 g/cm³ |
Sourcing either grade?
Nasteel stocks both families from Shenzhen with EN 10204 3.1 mill certificates by heat number.
Ask for a quotationSee full data sheets: API C90 Casing · API L80 Casing. Substitution decisions for certified parts stay with the design authority.